Hi lostandconfused6,

I don't think that you're overreacting, considering the history that they have together. I'd feel frustrated if my partner was trying to defend someone that he was casually with and say that their friends. I can understand if it was an exgf and they were on friendly terms. BPD is an attachment disorder, a pwBPD will quickly attach to someone and won't completely detach from someone, I'm not saying that this is the case with your boyfriend and this person because I don't know their r/s.
As you already know, a core criterion for BPD abandonment, abandonment fears, the core wound of abandonment, a pwBPD will try to create exit plans in their current r/s to circumvent being abandoned, perceived or real. This could be such a r/s, I'm not sure how attached she is with him, but if they've been friends for 21 months that raises red flags. What do you think?
I think this girl is still holding on to the glimmer of hope that 1 day they will be something despite what he tells her... .and he doesnt see it that way to say he has few friends is an under statement he really has none other than that girl and the friends i have introduced him to. I think he doesn't quite grasp the boundaries of a friendship. I also don't think this girl is all there mentally from what i've been told by a cousin of hers and people that have known her through out the years. My boyfriend says the same thing she's very stupid and doesn't understand basic concepts or normal ways of thinking. He thinks her randomly popping up at his house 2 or 3 times a week for 15 or 20 min is no big deal i see it as a huge deal. He brought it up to his mom that this girl needs to be limited on her access to their house, her reply "i'm 61 you arent going to tell me who can and can't come in my house tell c____ to go control someone else" a reaction much like he would have which raises more questions about his mom possibly being BPD as well. She also doesn't know the extent of what happened between my boyfriend and the other girl. I know if i tell him it's me or her he will go in one of his moods and nothing will be accomplished. This girl is nothing compared to me in any aspect looks, brains, personality, success, or family. I also fear that he feels he deserves someone like her and that's why he keeps her around he has told me many times that he feels he doesnt deserve me because of where he is in life.
I know for a fact that i am the only person in his life willing to do what i have to in order to help him through this and support him while he finds the right treatment for his BPD but i also feel i'm getting the short end of the stick. With our schedules and his disgusting selfish family that guilt trips him and manipulates him into doing things i get to see him 2 days a week 3 if i'm lucky. I feel like we make progress then he goes home and it's all erased. I have nicely asked him to adjust her friendship with him and not see her unless it's in a public place and keep communication to a minimum and some days he agrees then he gets in a mood and he tells me he will do what he wants. I try not to push but it's hard.